In the related art, when a dental material such as an orthotic material, a pit and fissure plugging material, etc., is adhered to unground enamel, an operative procedure for the adhesion has been employed according to which the dental material is brought into pressurized contact with or packed on the enamel surface to which acid treatment is applied by applying an acid etching material to the unground enamel, washing the enamel with water, and drying the enamel. With this operative procedure for the adhesion using the acid etching material, a roughly surface is formed by the demineralization of the enamel due to the acid etching material and adhesive performance is developed by micro mechanical fitting based on permeation and hardening of the dental material. The acid etching material is generally a liquid, therefore, it has excellent workability at the application step. However, the acid etching material has high fluidity and has a disadvantage that the acid etching material flows to and permeates into the outside of the target portion. Problems are therefore also pointed out such as induction of secondary dental caries due to exposure of the demineralized portion when the acid etching material flows to the outside of the target portion.
It is also pointed out that the organic component (collagen) in the dentine is denatured, the collagen shrinks during air-drying and the shrinked-collagen raises a degradation of the adhesive strength when the acid etching material is applied to the dentine after a cavity is formed.
In addition to the traditional method of causing a dental material to adhere to the tooth surface by applying a dental adhesive composition after executing the acid treatment using the acid etching material, an adhesion method has recently been proposed according to which the tooth surface and the dental material are adhered to each other by applying a dental adhesive composition without executing any acid treatment using the acid etching material. The dental adhesive composition used in this case has an adhesive monomer having an acidic group in its molecule (hereinafter, referred to as “acidic monomer”) blended therein and can thereby concurrently execute the acid treatment to demineralize the tooth surface and primer treatment to cause the monomer to permeate. As above, the dental adhesive composition is used that has a self-etching function of concurrently executing the acid treatment and the primer treatment.
When the dental adhesive composition having the self-etching function is used, no problem arises such as any excessive demineralization of the enamel and denaturing of the collagen of the dentine, and the operation of the dental adhesive composition is simple. Therefore, many product lines thereof are put in the market.
Recently, fluorine tends to be applied to tooth surfaces in dental clinics and toothpaste with fluoride tends to be used in brushing teeth in the home due to the improvement of the preventive attention by patients and dentists. Thus, a tendency is recognized to improve the acid resistivity of the tooth surface. In the case where the acid resistivity of the tooth surface is improved as above, it is worried that the adhesive strength is degraded when only the dental adhesive composition having the self-etching function is applied. Especially, for a pit and fissure plugging material or an orthotic material to be adhered to unground enamel, the application of only the dental adhesive composition having the self-etching function results in an insufficient demineralization action, and a serious problem of degradation of the adhesiveness arises.
With the above in the background, acid etching materials have been proposed as follows whose damage to the tooth surface due to the demineralization is reduced by reducing the acidity thereof.
For example, Japanese Patent Publication No. 5-163111 proposes a technique according to which stimulation to the tooth pulp is reduced by retaining partially a dentinal plug that is present on the dentine surface after formation of a cavity by using a dental pre-treatment agent including a water solution of organic carboxylic acid and iron phosphate. Japanese Patent Publication No. 5-246817 proposes a technique according to which any excessive demineralization of the dentine after formation of a cavity and the tooth pulp damaging property is weakened by using a dental acid treatment agent formed by solving a polymeric compound that has a carboxyl group in its molecule and whose molecular weight is 1,000 to 500,000 into water, alcohol, or a solvent mainly including a mixture of these. With these techniques, however, the damage to the dentine is reduced weakening the acidity while a problem rises that the adhesiveness is insufficient for the unground enamel or the enamel after the formation of the cavity.
Japanese Patent Publication No. 10-81611 proposes a technique according to which the denaturing of the collagen in the surface layer of the dentine after the demineralization is suppressed and adhesion inhibition due to shrinkage of the collagen is prevented by using a dental pre-treatment agent including an acidic water solution that has a phosphate solved therein and whose pH is equal to or lower than three. With this technique, however, the acidic water solution is used whose viscosity is low and whose permeability into the dentine is high, and the demineralized portion therefore is not limited to the inside of the surface layer of the dentine and reaches a deep portion thereof. As a result, a problem arise that a damaging action for the tooth pulp, etc., tends to be generated.
On the other hand, Japanese Patent No. 3505182 discloses a technique that high adhesive strength for enamel and dentine is obtained simultaneously with facilitating a polymerization reaction of a dental adhesive composition used after acid treatment, by adding a polymerization catalyst to an acid etching material. Similarly to the invention of the above '611 publication, the invention of the above '182 publication provides a treatment agent whose viscosity is low and whose permeability into the dentine is high, and the demineralized portion therefore is not limited to the inside of the surface layer of the dentine and reaches a deep portion thereof. As a result, a problem arises that a damaging action for the tooth pulp, etc., tends to be generated. Similarly, when this treatment agent is used for the enamel, a problem is recognized that this treatment agent tends to excessively demineralize. With the invention of the above '182 publication, a problem arises that the adhesiveness is significantly degraded for either the dentine or the enamel depending on the type of used polymerization catalyst.